Florfenicol is a dedicated animal chloramphenicol broad-spectrum antibiotic researched and developed by Nagab-hushan of Schering-Plough Company in USA at the end of 1970s. In view of the prevention and treatment of animal diseases, the efficacy of florfenicol is better than that of chloramphenicol and thiamphenicol, so that the florfenicol has wider application prospect, and the synthesis of the florfenicol is always greatly emphasized.
At present, there are mainly two methods for industrially producing the florfenicol both at home and abroad: 1, D-4-Methylsulfonylphenyl serine ethyl ester is sequentially subjected to a reduction reaction, a reaction with benzonitrile to prepare oxazoline, a fluorination reaction in the existence of an Ishikawa reagent, a hydrolysis reaction, and a dichloro acylation reaction to obtain the florfenicol, namely, a synthetic route 1; 2, D-4-Methylsulfonylphenyl serine ethyl ester is sequentially subjected to the reduction reaction, the reaction with dichloroacetonitrile to generate oxazoline, the fluorination reaction in the existence of the Ishikawa reagent and the hydrolysis reaction to obtain the florfenicol, namely, a synthetic route 2. The dichloro acylation reaction is omitted in route 2 relative to route 1, so that route 2 effectively reduces production and operation steps and cost.

D-4-Methylsulfonylphenyl serine ethyl ester is used in the above-mentioned two synthetic routes; however, the existing industrial method for preparing the compound is still to adopt tosyl chloride as a starting raw material to have the reduction reaction, a methylation reaction, a bromination oxidation reaction and the hydrolysis reaction to obtain P-methylsufonyl benzaldehyde, then the P-methylsufonyl benzaldehyde is used for reacting with glycine and copper sulfate to prepare a copper salt, and the copper salt has an esterification reaction and is resolved by tartaric acid to obtain D-4-Methylsulfonylphenyl serine ethyl ester, namely, a synthetic route 3.

The production technique involved in route 3 can produce a great amount of copper sulfate waste water in the production process, so that the treatment cost of the waste water is very high; moreover, 50% raw materials are wasted due to the chiral resolution on the aspect of the atomic economy, and production and operation are time-consuming; and the introduction of fluorine atoms uses the Ishikawa reagent which can severely corrode the equipment and is relatively high in cost.
In recent years, the research on the asymmetric reduction synthesis of a chiral compound by utilizing a chiral catalyst is widely performed, and relevant research on the florfenicol is also carried out. The applicant devotes to the research on preparing the florfenicol through the asymmetric reduction reaction by utilizing the chiral catalyst: CN102827042A discloses a scheme for taking thioanisole as a starting raw material to synthesize the compound [1-benzylaziridin-2-yl][4-(methylmercapto)phenyl]ketone through the three-step chemical reaction, further for performing the asymmetric hydrogenation reduction reaction for a product by utilizing the chiral catalyst to obtain [1-benzylaziridin-2-yl][4-(methylmercapto) phenyl]methanol, and further for preparing the florfenicol by means of several chemical reactions, wherein the chiral catalyst used in the scheme is trans-RuCl2[(R)-xylbinap][(S)-DPEN]. In the scheme, chiral central carbon is built by utilizing the asymmetric reduction reaction of the chiral catalyst, so that the chiral resolution is avoided. However, the chiral catalyst itself has the weaknesses of difficulty in preparation and storage, easiness in inactivation in industrial production, etc., further resulting in high application cost and disadvantage to the industrialized production. In view of this, it is very necessary to find a production route more suitable for industrialization.